Once film has been developed and fixed, it is no longer light-sensitive in the way unprocessed film is. Before processing, the emulsion contains light-sensitive silver halide crystals that record the image when exposed in the camera. During processing, development turns the exposed crystals into image-forming metallic silver, and the fixing step removes the remaining unexposed silver halides. After that, there is no longer any significant light-sensitive material left to fog from normal viewing.

That’s why developed negatives and slides can be examined in daylight, held up to the sun, and printed or scanned later without being “re-exposed” like fresh film. You still want to handle them carefully to avoid scratches, dust, fingerprints, heat, or long-term fading, but ordinary daylight inspection will not destroy them.